sedimentary
Chert (River Pebble)
Cryptocrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness: 7 Mohs; Color: Tan to brown; Luster: Waxy to dull; Crystal structure: Trigonal; Cleavage: Conchoidal fracture; Specific gravity: 2.65
- Hardness
- 7 Mohs
- Color
- Tan to brown
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 Mohs; Color: Tan to brown; Luster: Waxy to dull; Crystal structure: Trigonal; Cleavage: Conchoidal fracture; Specific gravity: 2.65
Formation & geological history
Formed via the accumulation of silica-rich microfossils or chemical precipitation in marine or freshwater environments. This specimen was likely smoothed by fluvial action (river transport).
Uses & applications
Historically used for stone tools/flintknapping; currently used in decorative landscaping, as road base, or for polishing in rock tumblers.
Geological facts
Chert and flint are essentially the same material; the name 'flint' is usually reserved for dark varieties found in chalk beds. It is one of the most durable sedimentary rocks.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and smooth, rounded water-worn texture. Commonly found in riverbeds and gravel pits.
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